At FULL Charge Multiplus is giving >>> Low Battery Alarm (Battery Low Voltage) >>> & shutting down

DIY
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Multiplus 3000VA 12V/120AMP + Smart BMS CL - Smart Shunt + and Cerbo GX + Smart Lithium LiFePO4 Batteries + Smart Solar MPPT 100/50

Every time we try to use our water kettle (which pulls 1500W at 120V) we get a shutoff triggered by the alarm. We have been using this system without issue since 2/3/24 it is now 6/1/25 and we are facing this low voltage alarm.

We brought our SOC to 100% by charging all the 4 cells to 3.55Veach 14.2V battery on alternator/solar. Plus we also updated all the firmware.

Judging by the graphs I don’t even think the voltage is going low enough to trigger the alarm because our low batter voltage alarm is set to 12.4V

Please help us understand why this is happening after a 16 months of no issues.

Thank you!

EDIT: After further investigation into the VRM data I noticed that the first time this alarm occurred there was a voltage drop between the Battery Voltage (12.85V) and VE. Bus DC Voltage of the Inverter (12.15V) (see first pic)

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Furthermore, after the first incident and fully charging the battery with solar and alternator charging we still have the issue and I noticed in the VRM data that the AC Output Voltage of the inverter drops significantly from 120V to (when the water kettle is turned on) 68V (see next three pics for before, during, and after alarm readings)

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Screenshot (15)1920×1042 144 KB

Screenshot (16)
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Screenshot (17)
Screenshot (17)1920×1046 148 KB

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Your first thing to do is to check the wiring between the batteries and the inverter for loose connections, frayed wire, isolators that are not making good contact, partially blown / corroded / broken fuses etc. I am assuming that this is a mobile application judging by the use of the CL BMS and most cases of low voltage are connections coming loose from engine / vehicle vibration. Put the system under some load that it will sustain then use a multimeter to check the voltage at each connection. The issue may be in the positive or the negative cable.

3

Thanks for the reply pwfarnell! I am going to give the system an inspection looking over the potentials you pointed our and test again / post an update.

I appreciate your help!!